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Relief valve

347 Member Posts: 136
Hello All,
I have a customer who has an oil fired boiler with a Williamson 46 gallon indirect water heater. His relief valve keeps popping off every few days. Oil company replaced the relief valve, fill valve and extrol (set close to 15 PSI). The problem keeps happening. The indirect has been checked of leaks (back filling the boiler) and is fine. The water feed valve has been turned off for a while now and the relief valve keeps popping off.
I placed a pressure gauge with a pressure spike needle on one of the zones to check it against the boiler gauge, they both are reading the same pressure, around 15 PSI.
I was at his house the other day about an unrelated issue and found the gauge spiked to over 60 PSI. After resetting the needle to 15 PSI. While working near the boiler (which is only making hot water now), it turned on and gauge spiked to 80 PSI, while the pressure gauge only went to about 29 PSI and the relief valve started to trickle.
Could the circulator for the indirect (Taco 0011) add that much pressure to the system to pop the relief valve?
I can not think of anything else that could cause this. I hope someone can think of something that I'am missing.


  • BillyO
    BillyO Member Posts: 276
    heat exchanger in storage tank have a hole in it possibly
  • Zman
    Zman Member Posts: 7,447
    BillyO said:

    heat exchanger in storage tank have a hole in it possibly

    I think that the indirect needs to be revisited. The 0011 can build 15 psi in a worse case scenario. Pressures as high as you are seeing are not possible from a 0011.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • 347
    347 Member Posts: 136
    The indirect was tested over a 24 period and the pressure on the test gauge remained at the test pressure.
    EBEBRATT-Ed Member Posts: 13,460
    Circ pump could not possibly do that.

    Obviously something wrong. To get to 80psi if it really is getting there which i doubt (i suspect you gage with the spike needle is lying to you.)

    You say they installed a new feeder and set to 15 psi but did they check the expansion tank pressure with it removed from the system? You could have a bad tank.

    also check the city water pressure and see if it is 80psi, thats high.

    With the city water feed isolated (and assuming the shut off valve is tight), a good expansion tank, the indirect is about the only issue. You could have a valve some where maybe leading to the expansion tan that looks open but may be closed ...broken internally
  • Jamie Hall
    Jamie Hall Member Posts: 21,117
    Whoa. Step back and think a bit. First off, as has been said the circulator pump can't produce anything like that much pressure -- so write that off right away.

    Now: there are only two ways in which the pressure in a hot water heating system can increase: either the expansion tank is not doing its job or something, somewhere, is adding water to the system from a higher pressure -- such as the domestic water supply.

    So. The expansion tank. Does it have a valve connecting it to the system? Is the valve open? It is? OK, close it, drain the tank and check the precharge. It should be 15 psi. If the tank won't hold air, it's junk. Reconnect the tank -- or a new one, if need be -- after setting it to the correct precharge.

    Observe the pressure over time with the boiler turned off. It should not change at all. If it rises, even slowly, water is leaking into the heating system from the domestic water, Tracking that down is mostly a matter of finding out where it's coming from, and the most likely candidates are a leak in the indirect or a valve not fully closed or leaking by. Shouldn't take long to find it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • neilc
    neilc Member Posts: 2,196
    could the boiler have sediments within, and be "kettling",
    and blowing off steam expansion?
    known to beat dead horses
  • Zman
    Zman Member Posts: 7,447
    Does the house have a pressure reducing valve and backflow preventer where the main comes in? Is there an expansion tank on the domestic water system.
    I am wondering if you are seeing extreme pressure in the domestic piping that is intermittently pushing through either the boiler fill or indirect. Moving your pressure gage to the domestic side might be telling. I have seen domestic pressure >160 PSI caused be either city water systems or thermal expansion.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    HVACNUT Member Posts: 5,038
    > @347 said:
    > The indirect was tested over a 24 period and the pressure on the test gauge remained at the test pressure.

    Where was the gauge? On the indirect's HX side or the boiler side? I agree. Look at the indirect again. If with boiler maintained 15 psi with the indirect isolated, then...
  • unclejohn
    unclejohn Member Posts: 1,830
    Was the boiler fired when the indirect was tested. May only leak when hot or run for a while like during a shower or clothes washing.
  • HomerJSmith
    HomerJSmith Member Posts: 2,156
    edited June 2020
    I assume you checked the name plate rating of the components that were replaced by the oil company and that they are correct.

    There can be only two causes. 1 The pressure is coming from the street main, 2 the boiler is creating the increase in pressure when it's firing.

    I would like to verify the air charge on the Extrol, like Reagan, "Trust but Verify" and the work done by the oil company.

    That both gauges read the same is as it should be and indicate to me that the street main isn't the problem. The boiler is the problem. Could the boiler be flashing? What could be the cause of flashing? Blockage of the flow because of a bad circulator, but I would suspect the boiler reaching hi-limit cutout before flashing occurs. Also, a mineralized heat exchanger creating micro flashing which would increase pressure without reaching hi-limit. What is the quality of the water?

    Very curious, hmmm.

    Tridicator reading are inaccurate after a number of years. What is the temp and pressure reading while your watching the gauge when it is firing?
  • 347
    347 Member Posts: 136
    Ebebratt-Ed- I'am making an assumption that my pressure gauge is right. The red needle did get up to 80 PSI. Why it hit there, I don't know, but something made it go that high.
    AS per the homeowner the company did check the pressure on the extrol tank before they installed it ( He called the company and they said that's how they "always" install them). I did not take it off the system to check it. I will try and get back there this week to check. Your right it could be bad.
    I will also check the domestic incoming water pressure. The boiler inlet water valve is a ball valve and I assume that it holding.

    Jamie- I was pretty sure that the circulator could not add that much pressure to the boiler (while running), but I was not sure about a quick jump in pressure when it first starts. Maybe starting and stopping throughout the day and adding a little higher pressure over the course of time would increase the boiler pressure and pop the relief valve?
    The indirect was isolated from the boiler piping (and the boiler feed valve was closed) and a gauge was installed on the boiler side and over the course of about 24 hrs the pressure gauge did not rise.

    Neilc- I did not hear any "kettling" sounds when the boiler fires.

    Zman- I do not remember seeing a pressure reducing valve or backflow on the main. I will see what the city pressure is.

    I feel it is the indirect also. My problem is that the relief valve does not pop -off everyday. The homeowner tells me the bucket he has to catch the water is dry sometimes 2 days and sometimes 5 to 6 days. from what I'am hearing it not a steady problem (like very day or so).
    If the indirect does have some type of pin hole in the coil, wouldn't the relief valve pop-off on regular basis? like every 10 hrs or so? If the indirect is bad with a slow leak, what would make gauge spike that high? I would think even if the city pressure is that high it would take a while to reach not in a matter of minutes (10 or so).\
    Thank again
    EBEBRATT-Ed Member Posts: 13,460
    @347 can't make any assumptions. Circ pumps don't increase pressure they just move the water around
  • BillyO
    BillyO Member Posts: 276
    I have seen this before so don't crucify me , are connections to domestic and heat exchanger correct?
  • clammy
    clammy Member Posts: 2,916
    Has any work been done to the home ,bathroom renovation or work to potable water piping . It could be possible there’s a cross connection between potable and your heating systems piping . It happens also have you ran the boiler and checked for the proper operation of its limits and controls including tank aquastat and ensure that it’s not being over heated . I would really look into cross connection some where . Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • lchmb
    lchmb Member Posts: 2,997
    does it have a spirovent and is it plugged? I've seen where sediment (old radiant tubing failed) plugged off the screen and cause's the system to act up like your describing..
    Alan (California Radiant) Forbes
  • 347
    347 Member Posts: 136
    Thank you all your responces. I owe everyone an apology.
    I went back today and checked the indirect myself and it is leaking into the boiler.
    The thing I learned, check out things yourself and don't take someone else word for it.
    Thanks again for all your help.

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 5,658
    edited June 2020
    You should check the water heater. I think there is a hole in the heat exchanger inside the tank
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • BillyO
    BillyO Member Posts: 276
    haha, sounds familiar